CNC Thread Mill Programming
Programming the Correct Tool Path
Do not radial infeed the mill. Thread mills generate
high radial forces or "side load pressure". This is due to the
"V" form ground on the periphery of the tool. If a thread mill
has a 1" length of cut, the effective length of cutting edge engagement
is approximately 2". This is the standard length of thread on a 3/8"
diameter tool. This equates to a 5.33 length to diameter ratio.
Any effort to avoid immediate side loading to the tool
will prevent the possibility of tool breakage or chipping. If a radial
infeed is performed, the tool has to come to a complete stop before the
360° arc rotation is performed. Generally, a broken or damaged tool
will be the result. Widia GTD (formerly Greenfield) highly recommends the use of a small arc
into the part following the helix of the thread to be produced, then the
360° arc around the center of the hole, and completing the operation
by arcing away from the threads to blend the thread.
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